By contrast, in the two-bogie inspection car, the car is arranged in the
same way as the passenger train, as shown in Fig. 4. Rail
displacement is detected at three axis positions. This will show track
displacement, as shown in Fig. 5. This is called asymmetrical chord
offset method. From the result of measurement according to the
asymmetrical chord offset method, the 10-meter chord versine
displacement used for practical track maintenance is calculated using
the digital filter treatment method.